1. Field of the Invention
The present invention relates to a magnetic recording-reproducing apparatus using a helical scan system for recording and reproducing data on a magnetic tape by winding the magnetic tape around a rotary head drum, and also relates to a method of detecting dew condensation in the magnetic recording-reproducing apparatus.
2. Description of the Related Art
In a magnetic recording-reproducing apparatus using a helical scan system for recording and reproducing data on a magnetic tape by winding the magnetic tape around a rotary head drum, dew condensation may be observed on the rotary head drum when the magnetic recording-reproducing apparatus using a helical scan system is moved in a place with high temperature and high humidity. The magnetic tape is sometimes stuck on the rotary head drum to damage or break the magnetic tape or the rotary head drum when winding the magnetic tape around the rotary head drum with dew condensation. Therefore, dew condensation that may form on the rotary head drum may accurately be detected in advance and winding operation of the magnetic tape around the rotary head drum may adequately be controlled.
Dew condensation detection is generally conducted by locating a dew condensation sensor around the rotary head drum which indirectly detects the rotary head drum condition using the dew condensation sensor.
With such dew condensation detecting method employing such dew condensation sensor; however, the current state of the rotary head drum cannot accurately be detected since longer time would take to detect the dew condensation when a temperature drastically changes.
Japanese Unexamined Patent Publication No. 2004-192713 discloses an example of a recording-reproducing apparatus capable of detecting dew condensation formed on a rotary head drum in real time. According to such a recording-reproducing apparatus, dew condensation is detected by the following manner: a magnetic tape slightly contacts a rotary head drum before winding the magnetic tape completely around the rotary head drum; if dew condensation has been formed on the rotary head drum, there may be a change in the rotational frequency of the rotary head drum. Thus, it is possible to determine whether or not dew condensation is formed on the rotary head drum by detecting a change in the frequencies of the rotary head drum. When dew condensation has been detected on the rotary head drum, the magnetic tape will be unloaded from the rotary head drum.
However, in the dew condensation detecting method according to the related art, if dew condensation has not been detected from the rotary head drum with having the magnetic tape slightly contacting the rotary head drum, dew condensation may still be formed on the rotary head drum while a subsequent tape-loading operation is conducted. Thus, since the related art method cannot detect the above-described dew condensation, it is difficult to reliably prevent the magnetic tape or the rotary head drum from being damaged or broken.